Control valve arrangement for a hydraulic drive

ABSTRACT

First and second control units, having first and second control valves, are provided for connecting first and second pumps with a plurality of hydraulic first and second consumer motors, respectively. The units also include first and second switching valves which can be operated to supply pressure fluid from the respective first or second pumps to the second and first consumer motors, respectively, so that each consumer motor can be also operated with pressure fluid from both pumps.

United States Patent 1191 Distler 1 1 CONTROL VALVE ARRANGEMENT FOR AHYDRAULIC DRIVE [75'] lnventor: Josef Distler, Lohr/Main, Germany [73]Assignee: G. L. Rexroth GmbH, LQhr/Main,

' Germany [22] Filed: July 27, 1972 [2]] Appl. No.: 275,829

[30] Foreign Application Priority Data Aug. 4, 1971 Germany; 2138986 52u.s.c1. 1/411R,91/414, 60/421 51 lnt.Cl. ..F15b 13/06 [58] Fieldofsearch ..91/411R,414;60/421 [56] References Cited UNITED STATESPATENTS 12/1937 Henry 60/421 X 9/1964 Stacey 91/411 R 1451 Apr. 2, 1974Schuetz 91/414 X 3,258,926 7/1966 Junck et a1 1/411 R 3,350,986 11/1967Berta et a1. t 91/414 3,360,925 1/1968 Zimmerman.... 60/421 X 3,543,64612/1970 lijima 91/414 Primary Examiner-Edgar W. Geoghegan Attorney,Agent, or Firm-Michael S. Striker [57] ABSTRACT First and second controlunits, having first and second control valves, are provided forconnecting first and second pumps with a plurality of hydraulic firstand second consumer motors, respectively. The units also include firstand second switching valves which can be operated to supply pressurefluid from the respective first or second pumps to the second and firstconsumer motors, respectively, so that each consumer motor can be alsooperated with pressure fluid from both pumps.

7 Claims, 3 Drawing Figures PATENTEDAFR 2m 3800 669 SHEET 2 [1F 3 Fig.2

CONTROL VALVE ARRANGEMENT FOR A HYDRAULIC DRIVE BACKGROUND OF THEINVENTION pumps are supplied through two control units totwo groups ofhydraulic consumer motor which operate different parts of the machine.In the prior art, both pumps can be connected with a specific hydraulicmotor. Due to this fact, the efficiency and power of a dredging machinecan be substantially increased, and moreover the two pumps or othersources of pressure fluid, are economically used.

The connection of one pressure source to a consumer motor which isalready supplied with pressure fluid from another pressure fluid source,is carried out in the prior art by connecting conduits for connectingthe outlet of one control valve With the inlet of the followingcontrolvalve which isassociated with the respective consumer motor. The controlvalves must be large, since they have to control the double amount ofpressure fluid. The cost of such an arrangement is high, and storage ofdifferent types of valves and additional tools are required.

SUMMARY OF THE INVENTION It is an object of the invention to provide acontrol valve arrangement which includes inexpensively and easilymanufactured control valve units for driving hydraulic'con sumer motorswith pressure fluid from one or two sources of pressure fluid.

In accordance with the invention at least one control unit of twocontrol units which are connected with different pressure sources, hasan additional switching valve which can supply pressure fluid from onesource to a consumer motor supplied with pressure fluid from anothersource by meansofa control valve. Due to the direct connection of thepressure source of the respective other control unit to the respectiveconsumer motor, the control valve associated with the respectiveconsumer motor, need not be enlarged, so that the control' valves andswitching valves in each control unit may have the same size.

The use of an additional switching valve for supplying pressure fluidfrom a first source to a consumer motor supplied by a second source bymeans of a control valve in the respective other unit, results in aconsiderably reduced cost, as compared with the correspondingarrangement according to the prior art.

In a preferred embodiment of the invention, the additional-switchingvalve is the last valve in the respective control unit in downstreamdirection of the pressure fluid, and is connected in series with thepreceeding control valve of the respective control unit. In this manner,the respective switching valve can only connect the associated pressuresource with a consumer motor which is normally supplied by the othersource, if the upstream control valves permit such a pressure fluidsupply. When an upstream control valve of the same control unit isoperated to supply pressure fluid, the flow of pressure fluid to theadditional switching valve, which is arranged downstream of therespective control valves, is interrupted.

It is advantageous to use as control valves and switching valves, valvemeans which have a normal position of rest and two control positions,and whose valve body has six ports. The control valves, but not theadditional switching valves, of each control unit, are connected inparallel with each other between the respective pressure source and alow pressure discharge region such as a container with atmosphericpressure.

It is also advantageous when the series connected additional switchingvalve is operated at a different moment than the respective associatedcontrol valve of the respective other control unit. Due to this timedsequence, the fine adjustability of the hydraulic drive is not impairedby adding the flow of pressurefluid of the second source of pressurefluid.

In a specific embodiment of the invention, the additional switchingvalve has two control positions respectively connected with differentconsumer motors associated with the respective other control unit. Inthis event, the respective additional shifting valve is associated withtwo hydraulic motors which are, in turn, supplied with pressure fluidfrom two control valves of the respective other control unit. This hasparticular advantages if the control valves of one control unit areassociated with the cylinders of the consumer motors for the scoop andthe boom of a dredging machine. For increasing the working speed, thesecond source of pressure fluid is connected with the working chambersof the two consumer motors.

A particularly simple and advantageous construction of the control unitsis obtained if either chambers which communicate with the pressuresource, and are located adjacent other annular chambers connected withconsumer conduits, are connected by a channel which is located inanother plane than a channel which is located between the chambers whichcan be connected with the pressure source. This results in thepossibility to arrange the valve slide of the switching valve either inseries or in parallel with the respective upstream slides of the controlvalves.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction arid its methodof operation, together with additional objects and advantages thereof,will be best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic viewillustrating the hydraulic circuit of a control valve arrangementaccording to the invention which is particularly suited for a scoopdredging machine;

FIG. 2 is a longitudinal sectional view illustrating a control unit usedin the embodiment of FIG. 1; and I FIG. 3 is a fragmentary sectionalview illustrating a modification of the control unit shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, afirst pump or other source of pressure fluid P, supplies pressure fluidthrough a control unit I to hydraulic consumer motors F L and AT. Asecond pump or'source of pressure fluid P suppli% pressure fluid througha second control unit II to hydraulic consumer motors F,-, SCH, and S.

Control unit I includes control valves 1, 2 and 3 and a switching valve4, and control unit II includes control valves 5, 6, 7 and a switchingvalve 8. The hydraulic motors are used for operating a scoop dredging machine. Control valve 1 controls the left drive motor F,, control valve 2controls the scoop drive motor L, and control valve 3 controls the boomdrive motor AT. The operating conduits A and B of the switching valve 4are directly connected with the beam drive motor S, which is primarilycontrolled by the control valve 7 of the control unit II. The controlvalve 5 of control unit II controls the right drive motor Fr, thecontrol valve 6 controls the tilting drive motor SCH, and control valve7 controls the beam drive motor S independently of the positions of thecontrol valves 5 and 6.

The additional switching valve 8 of control unit II is connected by itsoperating conduit A directly with a cylinder chamber 9 of the hydraulicconsumer motor L, and operating conduit B is directly connected with thecylinder chamber 10 of the hydraulic consumer motor AT. Each of thecontrol valves has three positions a, b, c, for connecting three pairsof ports with different connections. All valves are shown in the normalposition b in which connection between pump P, and pump P,, with therespective hydraulic motors is interrupted while the pumps P, and P,,are respectively connected with an open container T or other lowpressure discharge area. In the two other operative positions a and c ofthe control valves 1, 2, 3, 5, 6, 7, the respective associated consumermotor is supplied with pressure fluid from pump P and pump P,,,respectively, the flow being reversed when the control valve is shiftedfrom the position a to position 0, as indicated by arrows. The actualconstruction of the control valves will be explained hereinafter withreference to FIG. 3.

In the control positions a and c of switching valve 4, the operatingconduits A and B of switching valve 4 are connected with the cylinderchambers S and S of the hydraulic motor S so that pressure fluid fromthe first pum p P, is supplied to the hydraulic motor S which isprimarily driven by pressure fluid from the second pump P,,. In the samemanner, the switching valve 8 connects in the two control positions aand c, to the operating conduits A and B which supply pressure fluidfrom the pump P to a cylinder chamber 10 or 9 of the hydraulic motorsAT, L which have a piston and piston rod 12 and 11. As explained above,hydraulic motors AT and L are primarily controlled by control valves 3and 2 respectively which direct pressure fluid from pump P, to saidmotors.

In the control position a of switching valve 8, the pressure source P,,is connected by operating conduit B with the cylinder chamber 10 on oneside of piston- 12 of motor AT, while in the position 0, pump P,, isconnected by operating conduit A with cylinder chamber 9 of motor L.When control valve 2 is shifted to the position a, while the switchingvalve 8 is placed in the control position c, hydraulic consumer motor Lis supplied with pressure fluid from both pumps P, and P,, to cause anoutward movement of piston rod 12. When control valve 3 is shifted fromthe position b to the operative position a, and when the switching valve8 is shifted from the position b to the control position a, the cylinderchamber 10 of the hydraullic consumer motor AT also receives pressurefluid from both pumps P, and P,, so that the piston rod 12 is moved atan increased speed.

It is, of course, possible to connect the operating conduit A ofswitching valve 8 with the cylinder chamber 13 on the other side of thepiston 12 of the consumer motor AT, so that the consumer motor AT can beoperated in both directions by both pressure sources P, and P.

In the illustrated hydraulic circuit, it is not possible to connect bothpumps to the consumer motors P,, P,.

and SCH, but consumer motors L, AT, and S can be either operated bypressure fluid from one pump only, or by pressure fluid from both pumps,depending on the position of the switching valves 4 and 8.

In the illustrated normal position b of all control valves and switchingvalves, the respective pump P, or pump P,, is connected with thedischarge container T. If one of the control switches is shifted to anoperative position a or c, the flow of pressure fluid to container T isinterrupted, and the pressure fluid supplied to the hydraulic motorassociated with the respective operated control valve.

The pressure ports p of control valves 1, 2, 3 of control unit I, areconnected by a conduit 15 and branch conduits 15a, 15b directly with thepressure conduit 16 of the pump P,. The pressure ports p of controlvalves 5, 6, 7 are connected in the same manner by a conduit 19 andbranch conduits 19a, 19b with the pressure conduit 20 of the pump P,,.The pressure ports p of the switching valves 4 and 8 are connected byconduits 17 and 21, respectively with connecting conduits l8 and 22,respectively which communicate with the pumps P, and P,, respectively.Consequently, the switching valves 4 and 8 can only be connected withthe pumps P, and P,, when the control valves 1, 2, 3, and 5, 6, 7,respectively are in their normal positions of rest b. Conduits 25 and 26connect other ports of the control valves 1, 2, 3 and 6, 6 7 with thedischarge conduits 27. The control valves 1, 2, 3 are connected inparallel to pump P,, and the control valves 5, 6, 7 are also connectedin parallel with the pump P,,. The control valves and the switchingvalve of each control unit I and II are connected in series so that theswitching valves 4 or 8 are connected with the pump P, or pump P,, onlywhen the control valves are in the normal position b. Switching valves 4or 8 are separated from the pumps P, and P,,, respectively when one ofthe control valves 1, 2, 3 or 5, 6, 7 are shifted out of the normalposition of rest.

The shifting of the switching valve 4 for supplying pressure fluid frompump P, to the consumer motor S in addition to the pressure fluid ofpump P,, takes place a small time period after the associated controlvalve 7 has been operated to drive consumer motor S with the fluid frompump P,,. In the same manner, the switching valve 8 is operated afteroperation of the control valve 3, or of the control valve 2 to supplyfluid from pump P,, additionally to consumer motors L and AT,respectively. Due to this arrangement, the time adjustment of theconsumer motors is not disturbed by the adding of the flow of pressurefluid by the pump of the respective other control unit.

As shown in FIGS. 2 and 3, respectively, each control unit I or II, hasa cylindrical cast housing which is penetrated by four transverse bores31, 32, 33 and 34. The bores 32, 33 and 34 receive the valve slides 35,36, 37 which establish together with ports in the cylindrical bores, thecontrol valves 1, 2, 3, or 5, 6, 7, respectively described withreference to FIG. 1.

The valve slide 38 received by the cylinder bore 31 constitutes theswitching valve 4 or 8, respectively. The pressure fluid inlet P isprovided at one end, and the discharge outlet T is leading to thedischarge container T is provided at the other end of the housing 30.The inlet P which is connected with one of thepumps P, and P opens intoa cavity 40 which communicates with two longitudinal channels 41 and 42which connect annular chambers 43, 44, 45 and 46, 47, 48, respectively.Consequently, these chambers are filled with the pressure fluid. Otherannular chambers 50, 51, 52 and 53, 54, 55 surrounding valve slides 37,36, 35 are connected with operating conduits, not shown in FIG. 2which'are connected with the consumer motors.

Two channels 56 and 57, communicating with dischargeoutlet T connectannular chambers 58, 59, 60, 61 and 62, 63, 64, 65, respectively.

In the illustrated normal position of rest b of the control valve slides35, 36, 37, the annular chambers to are separated from the adjacentannular chambers which communicate with the discharge outlet T and withthe pressure inlet P. I

The annular chambers to 77 are connected b channels 78 to 81, andportions of the valve bores. Consequently, the pressure inlet P isconnected with the pressure outlet T and circulation in the control unitcan take place'without pressure. The valve slide 38 of theswitchingvalve 4 or 8 is surrounded by two annular chambers 87 and Y88 whichrespectively communicate with the operating conduits A and B which areconnected with the respective consumer motors. Adjacent the annularchambers 86 and 87 other annular chambers 88 and 89 surround valve slide38. Chambers 88 i and 89 are connected by a channel 90 which is locatedin another plane than the channel 81 which connects the chambers and 77.Channels 81 and are connected by a bore 91, so that in chambers 88, 89the same pressure prevails as in channel 81, which is connected with theannular chamber 75.

When the valve slide 38 of a switching valve 4 or 8 is shifted in thedirection of the arrow 93, the annular recesses of valve slide 38connect the chamber 58 with chamber-86, and chamber-87 with chamber 89.At the same time, ,the communication between chambers 76 and 77'isinterrupted, so that the free flow from the high pressure chamber 40to-the discharge outlet T is interrupted, whereby in channel 81 andchambers 88 and 8 9 the pressure is increased to the pressure of therespective pump. Due to the connection of chambers 87 and 89 by therecess of valve slide'38, the operating conduit communicating withchamber 87 is connected with thepump and due to the connection of thechamber 86 with the chamber 58 through the recess 94 of the valve slide38, the operating conduit communieating with chamber 86 is connectedwith the discharge outlet T. l

If, for example,'the valve slide 35 is shifted in the direction of thearrow 96, the connection between the annular chambers .75 and 74 isinterrupted, so that channel 81 is separated from the pressure inlet P.The connection between channel 81 and the pressure source is alsointerrupted if the valve slides 36 or 37 of the respective controlvalves are shifted to one of the end positions thereof.

An effective control of the valve slide 38 is assured only in theillustrated position of the valve slides 35, 36, 37, since only in thisposition, the channel 81 which communicates with the annular chamber 77,is connected with the pressure inlet P. The annular chambers 43, 44, 45and 46, .47, 48 of the control valve slides 34, 36, 37 are directlyconnected by the housing channels 100, 101, 102, 103 and are connectedby channels 41, 42 in any position of the control valve slides with thepressure inlet P, and are connected in parallel, so that an effectiveshifting of one of these control valve slides, independently of theposition of another control valve slide, can be carried out. If morethan one valve slide is operated, the pressure fluid supplied throughthe inlet P is divided between the respective consumer motors.

Due to the fact that the connecting channel 90 is not directly connectedwith the housing channel 81, but by means of a transverse bore 91, thehousing chambers 88 and 89 of the shifting valve slide 38 can be alsodirectly connected with the pressure inlet, so that they are connectedin parallel to the pressure source, together with the respectivechambers of the other control valve slides. It is only necessary todevise a connecting bore 104 between the annular chambers 45 or 48 andthe channel 90, instead of connecting channel 81 with the channel 90.

In FIG. 3, the connection between channel 81 and the connecting channel90 is not obtained directly by a connecting bore, but indirectly bywidened cylinder portion 98 forming an annular space 99 between valveslide 38 and portion 98. The annular space 99 connects housing chamber77, which is connected with channel 81, with the annular chamber 88which is connected by the connecting channel 90 with annular chamber 89.

it will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofcontrol arrangements for hydraulic drives, differing from the typesdescribed above.

While the invention has been illustrated and described as embodied in acontrol valve arrangement for operating consumer motors selectively withpressure fluid from one pump, or from two pumps, it is not intended tobe limited to the details shown, since various modifications andstructural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:

1. Control valve arrangement for a hydraulic drive comprising at leastone hydraulic first consumer motor, at least one hydraulic secondconsumer motor; a first control unit including a first source ofpressure fluid, and at least one first control valve for controlling theflow of fluid from said first source to said first consumer motor; asecond control unit including a second source of pressure fluid, atleast one second control valve for controlling the flow of fluid fromsaid second source to said second consumer motor, a pressure conduitconnected with said second source, and a switching valve located in saidpressure conduit downstream of and connected in series with said secondcontrol valve, said switching valve being also connected with said firstconsumer motor and being movable between a normal position, and at leastone control position for connecting said second source with said firstconsumer motor whereby said first consumer motor can be operated bypressure fluid from said first source alone or by pressure fluid fromsaid first and said second sources; and another switching valve in saidfirst control unit and connected with said second consumer motor of saidsecond control unit, and movable between a normal position, and acontrol position for connecting said first source with said secondconsumer motor whereby said second consumer motor can be operated bypressure fluid from said second source alone or by pressure fluid fromsaid first and said second source.

2. Control valve arrangement as claimed in claim 1 wherein said firstand second control valves are connected in parallel between the firstand second source, respectively, and a low pressure discharge region.

3. Control valve arrangement as claimed in claim 1 and comprising meansfor operating said switching valve of said second control unit to moveto said control position at a time different from the time at which saidfirst control valve is operated.

4. Control valve arrangement as claimed in claim 1 comprising twofirstconsumer motors; wherein said firstcontrol unit includes two firstcontrol valves for controlling the flows from said first source to.saidfirst consumer motors, respectively, each first control valve beingmovable between an inoperative position and at least one operativeposition; and wherein said switching valve has two control positionsrespectively directly connected with said two first consumer motors.

5. Control valve arrangement as claimed in claim 1 wherein at least saidsecond control unit includes a substantially cylindrical valve bodyformed with an inlet for pressure fluid at one end, and with an outletto a low pressure region at the other end, with consumer conduitsconnected with said second consumer motor, with diametrical valvecylinder bores, and with duct means connecting said inlet, said outlet,said consumer conduits and said bores, each valve of said control valvesand switching valve including a valve slide located in one of saiddiametrical valve cylinder bores and having piston portions, said valvebody having annular chambers cooperating with said piston. portionsconnected with said duct means and surrounding said valve slides forestablishing different connections of said duct means between said inletand outlet, and said consumer conduits when said valve slides aredisplaced.

6. Control valve arrangement for a hydraulic drive comprising at leastone hydraulic first consumer motor and at least one hydraulic secondconsumer motor; a first control unit including a first source ofpressure fluid and at least one first control valve for controlling saidflow of fluid from said first source to said first consumer motor; and asecond control unit including a second source of pressure fluid, atleast one second control valve for controlling the flow of fluid fromsaid second source to said second consumer motor, and a switching valveconnected with said first consumer motor and movable between a normalposition, and at least one control position for connecting said secondsource with said first consumer motor whereby said first consumer motorcan be operated by pressure fluid from said first source alone, or bypressure fluid from said first and said second sources; at least saidsecond control unit including a substantially cylindrical valve bodyformed with an inlet for pressure fluid at one end, and with an outletto a low pressure region at the other end, with consumer conduitsconnected with said second consumer motor, with diametrical valvecylinder bores, and with duct means connecting said inlet, said outlet,said conduits and said bores, each valve of said control valves andswitching valve including a valve slide located in one of saiddiametrical valve cylinder bores, said valve body having annularchambers including a pair of first annular chambers communicating withsaid pressure inlet and surrounding the valve slide of said switchingvalve, a pair of second annular chambers communicating with said secondconsumer motor and surrounding said valve slide of said switching valveadjacent said first annular chambers, respectively, said valve slidebeing shiftable to connect said first and said second annular chambers,and a third annular chamber connected with said outlet and surroundingsaid valve slide of said switching valve, said duct means including aconnecting channel connecting said second annular chambers in the normalposition of said switching valve, and another channel connecting saidthird annular chamber with said inlet, said channels being located indifferent planes, and a duct connecting said channels.

7. Control valve arrangement as claimed in claim 6 wherein said valvecylinder bore of said switching valve has a widened portion between saidfirst and second annular chambers forming an annular gap with said valveslide of said switching valve connecting said first and second annularchambers and constituting said duct connecting said channels in allpositions of said valve slide.

1. Control valve arrangement for a hydraulic drive comprising at leastone hydraulic first consumer motor, at least one hydraulic secondconsumer motor; a first control unit including a first source ofpressure fluid, and at least one first control valve for controlling theflow of fluid from said first source to said first consumer motor; asecond control unit including a second source of pressure fluid, atleast one second control valve for controlling the flow of fluid fromsaid second source to said second consumer motor, a pressure conduitconnected with said second source, and a switching valve located in saidpressure conduit downstream of and connected in series with said secondcontrol valve, said switching valve being also connected with said firstconsumer motor and being movable between a normal position, and at leastone control position for connecting said second source with said firstconsumer motor whereby said first consumer motor can be operated bypressure fluid from said first source alone or by pressure fluid fromsaid first and said second sources; and another switching valve in saidfirst control unit and connected with said second consumer motor of saidsecond control unit, and movable between a normal position, and acontrol position for connecting said first source with said secondconsumer motor whereby said second consumer motor can be operated bypressure fluid from said second source alone or by pressure fluid fromsaid first and said second source.
 2. Control valve arrangement asclaimed in claim 1 wherein said first and second control valves areconnected in parallel between the first and second source, respectively,and a low pressure discharge region.
 3. Control valve arrangement asclaimed in claim 1 and comprising means for operating said switchingvalve of said second control unit to move to said control position at atime different from the time at which said first control valve isoperated.
 4. Control valve arrangement as claimed in claim 1 comprisingtwo first consumer motors; wherein said first control unit includes twofirst control valves for controlling the flows from said first source tosaid first consumer motors, respectively, each first control valve beingmovable between an inoperative position and at lEast one operativeposition; and wherein said switching valve has two control positionsrespectively directly connected with said two first consumer motors. 5.Control valve arrangement as claimed in claim 1 wherein at least saidsecond control unit includes a substantially cylindrical valve bodyformed with an inlet for pressure fluid at one end, and with an outletto a low pressure region at the other end, with consumer conduitsconnected with said second consumer motor, with diametrical valvecylinder bores, and with duct means connecting said inlet, said outlet,said consumer conduits and said bores, each valve of said control valvesand switching valve including a valve slide located in one of saiddiametrical valve cylinder bores and having piston portions, said valvebody having annular chambers cooperating with said piston portionsconnected with said duct means and surrounding said valve slides forestablishing different connections of said duct means between said inletand outlet, and said consumer conduits when said valve slides aredisplaced.
 6. Control valve arrangement for a hydraulic drive comprisingat least one hydraulic first consumer motor and at least one hydraulicsecond consumer motor; a first control unit including a first source ofpressure fluid and at least one first control valve for controlling saidflow of fluid from said first source to said first consumer motor; and asecond control unit including a second source of pressure fluid, atleast one second control valve for controlling the flow of fluid fromsaid second source to said second consumer motor, and a switching valveconnected with said first consumer motor and movable between a normalposition, and at least one control position for connecting said secondsource with said first consumer motor whereby said first consumer motorcan be operated by pressure fluid from said first source alone, or bypressure fluid from said first and said second sources; at least saidsecond control unit including a substantially cylindrical valve bodyformed with an inlet for pressure fluid at one end, and with an outletto a low pressure region at the other end, with consumer conduitsconnected with said second consumer motor, with diametrical valvecylinder bores, and with duct means connecting said inlet, said outlet,said conduits and said bores, each valve of said control valves andswitching valve including a valve slide located in one of saiddiametrical valve cylinder bores, said valve body having annularchambers including a pair of first annular chambers communicating withsaid pressure inlet and surrounding the valve slide of said switchingvalve, a pair of second annular chambers communicating with said secondconsumer motor and surrounding said valve slide of said switching valveadjacent said first annular chambers, respectively, said valve slidebeing shiftable to connect said first and said second annular chambers,and a third annular chamber connected with said outlet and surroundingsaid valve slide of said switching valve, said duct means including aconnecting channel connecting said second annular chambers in the normalposition of said switching valve, and another channel connecting saidthird annular chamber with said inlet, said channels being located indifferent planes, and a duct connecting said channels.
 7. Control valvearrangement as claimed in claim 6 wherein said valve cylinder bore ofsaid switching valve has a widened portion between said first and secondannular chambers forming an annular gap with said valve slide of saidswitching valve connecting said first and second annular chambers andconstituting said duct connecting said channels in all positions of saidvalve slide.